The present disclosure relates to a hydraulic control device for an automatic transmission to be mounted on an automobile, and in particular to a control device for a line pressure which is a hydraulic pressure for operating friction engagement elements of an automatic transmission.
In the related art, a primary regulator valve regulates a pump pressure from an oil pump to generate a line pressure. In the primary regulator valve, basically, an urging force of a spring and a throttle pressure from a throttle valve act against a feedback pressure of the line pressure acting on a spool, and the line pressure is set by a linear function defined by the minimum proof pressure and the maximum proof pressure (see Japanese Patent Application Publication No. 1-238750).
In general, the minimum pressure of the line pressure is set to be equal to or more than a hydraulic pressure that secures a minimum drive force (evacuation drive force) for ensuring vehicle travel in consideration of a failure.